The term codon refers to a sequence of three nucleotides in a messenger RNA (mRNA) that specifies the incorporation of a specific amino acid into a protein. The relationship between codons and the amino acids they code for is called the genetic code. The process of converting mRNA sequence information to the amino acid sequence of a protein is called translation. An anticodon is a complementary 3 base sequence in transfer RNA (tRNA).

Not all codons are used with equal frequency. In fact, there is a considerable amount of variation in the patterns of codon usage between different organisms.

1. Codon Usage Database

2. Transcription/Translation Summary